Thread-wound golf balls are generally prepared by winding a length of high elongation thread rubber around a core to form a core ball and applying a cover thereto. The cores used include liquid centers wherein a hollow spherical centerback of rubber or the like is filled in its hollow interior with water or liquid containing a specific gravity modifier and solid centers obtained by consolidating rubber compound. Since liquid centers are too soft to wind thread rubber thereon, liquid center cores are frozen and solidified with dry ice, liquid nitrogen or another refrigerant before rubber thread is wound thereon. Depending on whether the rubber composition is soft or hard, some solid centers allow a rubber thread to be wound thereon without freezing, but solid centers of relatively soft type compositions are frozen with an appropriate refrigerant prior to thread rubber winding. After winding of rubber thread on frozen cores, the cores are allowed to thaw and then enclosed in covers.
During spontaneous thawing of the cores having thread rubber wound thereon, the thread rubber layer circumscribing the core is cooled. Then ambient moisture condenses on the surface of core balls within about 3 to 10 minutes after the completion of thread rubber winding, wetting the core ball surface with water. If core balls whose surface is wet were subsequently provided with covers, shaping deficiencies like bears and voids would frequently occur in the cover shaping step and a loss of adhesion between the cover and the thread rubber layer would allow the balls to deform upon hitting.
One prior art approach to avoid such inconvenience was by allowing the cores having thread rubber wound thereon to spontaneously thaw and then drying the core balls to remove water from their surface prior to enclosing the core balls in covers. However, the time taken for the core thawing and core ball drying steps was as long as 3 to 14 hours though it somewhat varies with the season. The time required for thawing and drying formed a neck against the development of a continuous automatic process for the manufacture of thread-wound golf balls.
The present invention has been made to overcome the problems of the prior art and its object is to provide a method for preparing a thread-wound golf ball which features a substantial reduction in the core thawing time and eliminates the need for core ball drying, thus greatly contributing to the development of a continuous automatic process.